[GHC] #7080: Make RULES and SPECIALISE more consistent

[GHC]

#7080: Make RULES and SPECIALISE more consistent
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    Reporter:  simonpj           |       Owner:                  
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:  _|_             
   Component:  Compiler          |     Version:  7.4.2           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Changes (by akio):

 * cc: tkn.akio@… (added)


Comment:

 I experienced a situation where I wanted to write rules like this. I think
 it would be very useful if the rule was accepted, and worked by finding
 whatever (Monoid w) dictionary that is in scope. But perhaps I am asking
 too much of the simplifier?

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7080#comment:1>
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